text:
Was differential thrust used in the P-38 to improve turn performance?
In the P-38 Lightning could differential thrust be used to improve turn performance ? If so what was the procedure ?

I don't think this needs to be limited to the P-38, all twin engine aircraft with some distance between the wing mounted engines should exhibit the same behavior. I don't think it will though, given the dynamics of the turn force, you will be introducing significant yaw. What do you mean "turn performance"? Turn rate? or Radius?

Could it? According to what?

Ron Beyer. I meant both rate and or radius. Sorry for my imprecise language.

According to WW2 pilots, no. Aside from the dangers in adjusting 1600hp on one side of the aircraft on the fly in the midst of a dogfight... With the P38, they didn't need to. The P38 had an inherent advantage over single engine prop fighters of its era. Its engines (and propellers) rotated in opposite directions, canceling out any torque effect. The counter rotating engines and props were considered a big secret on the P38 when it was first designed. (as if anyone couldn't look at the angle of the props on each side and tell that.)
The pronounced torque of the 1600hp-2000hp single seat fighters played a major role in aircraft handling: both in takeoff and power on maneuvers, something WW2 flight simulators never seem to reproduce. Single engine fighters would roll left far quicker than they could roll right, due to the immense torque of the engine/prop combination, aiding in the left roll but inhibiting a roll to the right. This was most evident at lower altitudes, where the air is thicker and the torque effect more pronounced.
Not so with the P38 - contra rotating engines and props canceled the torque, and the P38 could roll right far quicker than any single engine fighter. While the P38 did have several issues at high altitude, WW2/Vietnam ace Robin Olds held that nothing could beat a P38... down low. (revisit the Dogfights/Air Ambush episode for that)
So, no, they didn't use asymmetrical engine power for maneuvering with the P38 - they didn't need to. Just roll right and turn - no single engine fighter of that day could stay with you.

Interesting that this answer is diametrically opposed by Spectre's new answer. Your answer was essentially "According to WWII pilots, no", while his is "According to WWII pilots, yes". I've got no clue who is right. If you have some links to back up your claim, that would give it much more weight.

I know this question was asked years ago. But yes, differential thrust was used and was a trick up the sleeve of 38 drivers. Irv Ethel used differential thrust to escape a gaggle of 109s over Africa after his flight was jumped near Lake Bizerte in Tunisia. He taught the maneuver to other 38 pilots who then used it both offensively and defensively. The idea was to chop throttle on the side that you wanted to roll to. This could be used offensively to beat an enemy aircraft into a split-s, or could be used to rapidly reverse direction as if spinning the plane around a vertical pole. The P-38’s counter-rotating props combined with the prop’s airflow over the wings, which supplemented lift at lower speed made the Lightning capable of fantastic low airspeed and high angle-of-attack maneuvers that single-engine aircraft watched in disbelief.

To be slightly more precise, the end effect is a yaw moment, not exactly roll. A rolling moment will also be induced depending on the place the engines are mounted and the general design of the airplane. In the same spirit, the rate of yaw (which is what a pilot will be interested in) will depend on so many parameters that one can speak only for a particular class of airplanes.

@ares "..chopt the throttle on the side that you wanted to roll to." seems pretty clear, there isn't a claim being made that differential thrust causes a roll.

Interesting that this answer is diametrically opposed to tj1000's answer. His answer was essentially "According to WWII pilots, no", while this one is "According to WWII pilots, yes". I've got no clue who is right. If you have some links to back up your claim, that would give it much more weight.

@FreeMan Here is Ethell's account of the event (originally published in Flight Journal.) It is not clear whether this became a common tactic.

Subtle distinction: the question (and to some extent, the "no" answers) address sustained turn performance; this answer addresses roll rate. Related, but not identical.

With hundreds (or even thousands) of pilots over the operational life of the P-38, it is no wonder that some pilots may have found differential thrust worthwhile and used it; and other pilots finding differential thrust not worthwhile.

@Koyovis, not only I understand it as a definite claim the differential thrust causes (or rather helps) roll, but it's the only reading that makes sense! The P-38 props spin inboard up, so by retarding the inside engine you get 1. the torque of the outside engine bank you into the turn and 2. the inboard wing losing some lift also banking you into the turn. There is also yaw effect but that is not useful in a high-G turn when the wings end up nearly vertical and most of the turning is done by the elevator. But a quicker roll into the turn can make a lot of difference in aerial combat.

@RalphJ, the question does not say “sustained”, just turn performance. And for fighters how fast it can initiate the turn, that is roll into it, is often even more important than the G it can pull.

What don't I understand? "Turn" is NOT roll. Everything about this answer is about the effect of differential thrust on roll rate, nowhere does it explain how this would affect turn, which is either turn rate (change in aircraft heading per second), or turn radius (the size of the turn circle you are moving on. Neither of these can possibly be affected positively by differential thrust.  I am downvoting.

@Jan Hadek, You are right, roll rate is important, but noting that it is important does not in any way mean that turn performance is better with a higher roll rate. Put Giant Ailerons on an F-104 and it will still take the whole state of Arizona to turn around. Engine thrust, and induced drag are also very important on turn performance, because they affect the ability to maintain a turn rate over a sustained period of time, but again, they are not the same thing as instantaneous turn rate.

The T-38 could roll at 720 degrees per second, but a Cessna 172 has a much higher turn rate and smaller turn radius. it appears to me you are not answering the question asked, but a different one, to wit, " ...  could differential thrust be used to improve combat maneuvering performance ? ..."  Now that question does include the concept of roll rate, engine thrust, and sustainability, as well as other factors.

Obviously, I am no stranger to grave digging.)
I noticed that for this question there is not a single reference in any of the existing answers and the top two directly contradict each other. While it is impossible to prove a negative (that no one ever used differential thrust in a P38 to improve handling) it is possible to look at how the aircraft was supposed to be used.
A 1943 P38 training video (essentially one long blur with narration) makes no mention of such a procedure. It does describe a means to increase maneuverability by using partial deployment of flaps as well as a mechanical stop for the flap control expressly designed for that purpose.
An exhaustively referenced P38 site describes the outward down rotation of the props as causing difficulty beyond that of a normal twin engine aircraft when a single engine takeoff occurs, as this exacerbates the effect of P factor. Combat pilots may make use of extreme characteristics to gain advantage, though this violent effect is not described anywhere on the site as being used in that way.

Losing one of two engines in any twin-engine non-centerline thrust aircraft on takeoff creates sudden drag, yawing the nose toward the dead engine and rolling the wingtip down on the side of the dead engine. Normal training in flying twin-engine aircraft when losing an engine on takeoff would be to push the remaining engine to full throttle to maintain airspeed; if a pilot did that in the P-38, regardless of which engine had failed, the resulting engine torque and p-factor force produced a sudden uncontrollable yawing roll and the aircraft would flip over and hit the ground.

This was a deliberate design decision and a change from early model's inward down as it increased the aircraft's stability as a gunnery platform.

The YPs were substantially redesigned and differed greatly in detail from the hand-built XP-38. They were lighter and included changes in engine fit, and the propeller rotation was reversed, with the blades spinning outward (away) from the cockpit at the top of their arc rather than inward as before. This improved the aircraft's stability as a gunnery platform.

Based on a different recommended means to improve maneuverability and the design choice of stability over single engine controllability, the use of differential thrust was not commonly used in flying the P38.

Is it safe to assume that the 2 quotes come from the linked site?

@FreeMan Yes. The page is huge so the quotes can be used to find the relevant section.

It depends how you want to turn I reckon. If by rudder only and if both engines are not flat out, then yeah you could up the outer engine thrust and yaw faster.
But that is an uncomfortable and slow way and generally not how it is done, usually pilots bank the aircraft, tilting the lift vector. That is a big vector and can provide much more centripetal force than the yaw scenario: the wings provide lift, and increasing the AoA a bit creates much more force.

The vertical tail is dimensioned to fly with one engine out, the wing is dimensioned to support the weight of the aircraft. Difference between engine thrust and weight is easily a factor 5, often more.

In flight, differential thrust has only adverse affect.  The only benefit of asymmetrical thrust would be to facilitate yaw in stalled condition or during taxi.
A stalled example of using asymmetrical thrust would be facilitating a hammerhead maneuver.

Hammerhead typically involves zero-lift a.o.a., not fully stalled a o.a..

Reading all this information on the question “ did pilots use differential trust during combat “
The answer is “ most likely not”
Although the p38 is one of the best fighter with two engines it will fly well on one and it could defend it self.
During combat you don’t like to lose speed.
Only if that energy is retained. Alt over energy.
Going slow the propeller factors (P factors  )
Is tremendous. Going slow and pulling one engine will render your plane uncontrollable for a brief moment. Loss of control is no good in battle .
Gong fast the yaw moment can be created bij rudders too. So why pulling that engine.
With rudders there is no adverse yaw. Just controlled yaw.
Going high and pull a engine is very unwise.
The plane fly true thin air, speed limits are totally different.   It can stall easily and or go transonic very quickly.  Meaning..there no place to go to un controlled flight.
At high altitude you keep the speed up to the best corner speed.
But maybe below 15000 ft pilots have used it.
low the air is thick and with some practice it could flip the plane like a snap roll or hammerhead. But please check that manual as airframe limitations are probably telling you not to.
Realise such an event is a wilde ride ..


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Where is the airport in Disneyland Paris? (DLP)
I just found out that there is an airport in Disneyland Paris with the IATA code DLP. Since I've never heard of it, I wanted to see it on Google Maps, but haven't found it.
Is there actually an airport, and where?
Why does Disneyland has its own, with CDG not far away?

Where did you find it? Is it really official? It does not seem to be listed in official-looking lists.

@JanHudec Actually I've found it in our database, as far as I know imported from some IATA file (obviously containing also non-airport entries, like I've found XED too).
One reference in the web I've found: http://www.flightstats.com/go/Airport/airportDetails.do?airportCode=DLP

I confirm, the nearest airport is CDG. You can then take a bus (called optile) and be there in about one hour, making an extra airport useless. But there is no IATA code DLP.

Is it possibly a heliport?

@ManuH Or the TGV, 15 minutes

I recall being told that disneyland has an IATA code so that your bags can be checked all the way to your resort hotel and you don't have to pick them up at the airport when you land.

This seems more about travel than aviation to me, although I can see why it might seem like an aviation question

IATA codes don't necessarily correspond to airports. Some non-airports have IATA codes to allow airlines to sell through tickets that might, for example, consist of travelling from A to B by plane and then onward from B to C by train. DLP isn't on Wikipedia's list of railway stations with IATA codes but I imagine something very similar is going on here.

Thanks for the information, I wasn't aware of it! I've found XED, which seems to be the railway station in Disneyland Paris.

Is there actually an airport, and where?

Disneyland does not have an airport in Paris,France.
Disneyland, Paris is situated approximately 20 miles from Paris.
There is a direct Shuttle Bus Airport Transfer to Disneyland from
(a) Charles de Gaulle,
(b) Orly and
(c) Beauvais airport.
http://vea-shuttle.co.uk/

I wanted to see it on Google Maps, but haven't found it.

Please check the Google Map here
http://www.airportia.com/france/disneyland-paris-airport/map/

Paris,France in case you confused it with Paris Hilton [ cit ]

@Federico: Or the wonderful Paris, Texas.

@mins how dare you leave out Paris, ID!

@FreeMan: This one is  well known in France, we know everything about it and the 504 souls who live there.

@mins that's fantastic!! Paris, ID is about a 2 hour drive from where I grew up. It's existence (along with Moscow, ID) helped impress my (then) college girlfriend (now wife)! She though I was quite the world traveler... It was a couple of years before I clarified her misunderstanding of "Paris" and "Moscow". ;)

@ah! I love these names. There is a story about Syracuse sung by a french singer in NY (in the 60s or 70s). But nobody could understand why he wanted to see Syracuse then Easter Island before dying...

Maybe for helicopters? Looking at google maps there seem to be helipads on one of the parking lots - https://goo.gl/maps/Z2BKE6aH7vF5tyCT9

closet airport for disneyland paris is cdg charles de gaulle.
also orly airport  cdg is most convient airport for dinsyeland paris
beauvais airport 130 km  fromdisneyland  ( special for rayan air )
private transfers from cdg to disneyland paris
Nearest Airport to Disneyland Paris

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What are the advantages of the angled flight deck layout used by some aircraft carriers?
I've been flying aircraft carrier approaches in a flight simulator lately and noticed that the carrier has an interesting layout. I have an image below where the landing runway is in red and the takeoff runway is in blue.

I can understand the takeoff runway - taking off into the wind with the catapult so that you can get enough air flowing to take off. The part that confuses me is the position of the landing runway. It is at a slight angle to the direction of the carrier's motion, meaning that when I fly the approach I have to aim to the right of the carrier and let it move underneath me. It seems to me as though this would just complicate an already difficult procedure, particularly in rough weather conditions.
Why not just take off and land in the same direction? As far as I am aware the aircraft only take off forward of the jet blast shields i.e. at the tail of the blue arrow. This would leave plenty of room on the carrier for landing. The only time I can think this would be a problem would be when a pilot needs to abort the landing and quickly take off again when there is another jet waiting to take off ahead of him, though this would assume that aircraft were taking off at the same time as others were landing (I have no idea if this actually happens).
It would be great if someone could shed some light onto why aircraft carriers have this layout - I'm not a pilot, just been playing around in simulator.

Do carriers conduct landings with the wind parallel to the ship axis or parallel to the angled flight deck?

@DJohnM one of the Naval Aviators on here will have a better answer, but as I understand it the carriers steam directly into the wind. That said, nuclear powered carriers are fast enough that they're mostly making their own wind. :)

@DJohnM They can't really make the wind go parallel to the angled deck, but some wind few degrees off straight is not that bad.

@SMSvonderTann.  Uhhh... Why not?  Just put a wind vane on the angled flight deck and turn the helm to keep it pointing straight down the flight deck, no?

@DJohnM That would not really work because the centre of rotation on the ship does not lie on the line made by the angled flight deck. It wouldn't be a good idea to keep a carrier running around in circles either.

You mean that for a constant actual wind direction, there is no constant course the carrier can steer that will have the apparent wind coming from 10 degrees to port of dead ahead?

@DJohnM Not if there's no wind. :) Remember that the carrier is moving. In calmish conditions, most of the "wind" will be coming from the fact that the carrier is moving forward at 30 knots (or whatever its speed may be.) You can make an airplane's course be 10 degrees off of its heading, but it's really hard to design a massive aircraft carrier to do that. You'd have to completely change the location of the screws.

This kind of layout is called the angled flight deck (also called 'skewed' or 'canted' deck) and was first used by Royal Navy. There are a number of advantages to this layout compared to using the same direction of landing and takeoffs:

It allows concurrent landings and takeoffs.
By having an angled deck, the aircraft which fail to connect (with the arrestor cables) during landing can go around and try again without risk of damage to other (parked and taking off) aircraft).

The main reason for the emergence of angled deck was the introduction of jet aircraft in naval operations, which due to their weight and high speeds required most of the deck available to complete an arrested landing. Also, in case of missed wires, it was possible to use a barrier in case of propeller aircraft, which was not possible in case of jet aircraft. According to Rear Admiral Dennis Campbell, the inventor of angled deck,:

But with the advent of the heavier faster jets, it soon became obvious that the dimensions of the carrier's deck would impose a limit to the standard of aircraft that could be operated. The inevitable increase in weight and landing speed of the jets would make it impracticable to retain the existing combination of arrester wires/barriers/and deck park without a drastic reallocation of the deck space required to absorb the much longer pull-out of the wires.

Prior to the application of the angled deck, this caused significant problems and requirement of complex machinery to overcome.

Ark sister ship and predecessor, the Eagle, was equipped with sixteen arrester wires and three different types of barrier (together with all their several hydraulic machines), and all this gear could only just cope with the first generation for (straight wing) jets.  No way would such a layout be good enough for the newer types.

The solution was to skew the flight deck by about 10 degrees (the HMS Ark Royal first had the flight deck angled by 5 degrees, which was then increased to 10) and use it for landing. This lead to:

The saving in arrester gear units and barriers – Ark needed only four wires and one (emergency only) barrier.  The reduction in weight and the extra space that this conferred enabled more mess-decks to be fitted in, thus reducing congestion in living spaces.
Since landing accidents would obviously be far less frequent, fewer aircraft and spare parts would be needed so costs would be greatly reduced.
Similarly, death and injuries to aircrew and deck handlers could be kept to a minimum – with a big boost to confidence and morale, not to mention the saving in training costs.
As experience was gained of the new scheme, less obvious advantages came to light.  New areas of parking, (abaft the island for instance); an added flexibility in the relative wind speed and direction, easier and faster deck handling, less wear and tear on the command, etc.

Perhaps surprisingly, though the USN has adopted this system in its supercarriers, the RN dropped it later on.

Well, the RN technically dropped "carriers" later on as well - their V/STOL carriers were officially 'through-deck cruisers', and according to Wikipedia "were built as aviation-capable anti-submarine warfare (ASW) platforms to counter the Cold War North Atlantic Soviet submarine threat". Different requirements, different design.

@egid Agreed. But what is surprising is that the new Queen Elizabeth Class Carriers doesn't look like they have angled flight decks.

They definitely do - or they could, were they to equip catapults and non-V/STOL aircraft. That was the original plan, from what I recall. If you look at a plan view, it's got the characteristic narrow bow deck with a port offset. They just haven't painted on the diagonal lines.

Early draft: https://s-media-cache-ak0.pinimg.com/736x/1c/3c/54/1c3c548363be0cf1fe63c82f3d8f5fdc.jpg

@aeroalias not at all surprising really - Britain's post war carriers were angled due to being intended for conventional air superiority/strike use, the Audacious class still having an angled runway. It's only the invincible class, designed for the Harrier, that weren't because in the 80s Britain was taking something of an anti-Soviet-submarine role in NATO strategy. That's no longer the case and so the newer carriers are reverting to a more typical use case (power projection/strike) which requires a fast-jet (angled deck) design

A co-worker friend of mine some years back was an ex-Navy pilot in the Korean War and years immediately following.  Having flown on both straight and angle deck carriers, his view was that the angled deck "tripled the life expectancy of a Navy pilot."  That would align with benefit #3. above.

An angled flight deck resolves many problems identified during WWII with carrier combat and flight operations (in addition to some of the other issues related to jet aircraft).
The first relates to the importance of not having a crash landing stop flight operations (or wreck staged/landed planes). For example, straight deck carriers often recovered planes in a fashion like this (images from Wikipedia, the USS Saratoga):

Notice the plane landing has a short distance to actually land/stop.
It is important to realize the implications of a crashed landing or an overlanding. A plane landing at this way, if it somehow jumped the barrier/missed/overshot is going to crash through many parked/staged planes. Clearing a flight deck, even with multiple elevators, is not instantaneous.
Next, let's consider the takeoff process. Again, look how many planes are staged on the flight deck:

This sort of operation was typical in the era before and during World War Two.
It's important to realize that most carrier configurations looked more like the ones here than what we think of when we think of a supercarrier when the angled flight decks were introduced. The experiences of those running WWII flight operations and the lessons learned drove the implementation of angled flight decks.
Imagine too if a plane returning to the ship suffers damages during landing or crashes. Given how the flight operations worked, this would prevent the ship from doing anything until the plane was dumped overboard/pushed out of the way. In a combat situation, precious minutes could mean the difference between a CAP being launched -- or no planes being launched.
Additionally, having two "runways" means multiple planes can be launched simultaneously. You get nearly twice as many launches per minute when having two runways.
The USN was already experimenting with multiple launch points with a hangar deck catapult with the Essex class:

While not wildly successful, it shows the USN was already interested in having multiple launch points for planes (don't try landing through this area!). These were all removed eventually during WWII but the need is indicated through their initial installation - six Essex carriers had hangar deck catapults installed.
Again, this indicates that there was a compelling problem to be solved with a straight flight deck and single launch/failure point.
Related to the increase in plane weights, having a longer "landing" zone allows heavier planes to actually accelerate upon landing in order to have enough airspeed to abort if needed. With either configuration as shown here, you would never want to be accelerating on landing if not required to prevent stalling - if you did you are simply increasing the risk of crashing into the other parked planes. Especially as plane weights increased and speeds increased, the risk of overshooting the barriers increased.
Another advantage is the increased ability for elevators to access the hangar deck. With a straight flight deck, you only can really have elevators that take away from your usable space. While the Essex class started this trend, having their elevators slightly sticking out from the ship, look at where the elevators were located in your image - they are completely out of the way of both flight decks. This is another advantage of the angled flight deck, because it means you can operate the elevators and use them to stage planes without significantly affecting flight operations. A straight flight deck has minimal ability for this.
Last for this mini-book, having two "flight decks" means that in a combat situation, a single bomb doesn't put your ship out of action. Many US carriers were put out of action temporarily from single hits to their flight deck. Having two "runways" means that you build in some safety in that you can use your ship to launch or recover aircraft even if you take damage (again, keep in mind that during these conversions WWII was fresh in the minds of designers/naval officers).

Nice answer with historical backing and an excellent selection of pictures. Not bad at all for your first answer here!

You don't really have "two flight decks". The catapults are well distributed, but there is just one set of arresting wires, so while hit to the bow disabling catapults 1 and 2 would leave 3 and 4 available, hit to the landing area still prevents all landings.

The angled part of the deck allows landing aircraft to go around if necessary as well as permitting simultaneous takeoffs and landings safely when that is necessary. As I understand it (perhaps a carrier pilot could enlarge on this), a carrier pilot wants a 4G landing impact. At the point of impact, he goes to full thrust so that if he doesn't catch a wire, he can safely fly off the end of the angled deck. If he does catch a wire, he immediately closes the thrust lever.
They don't flare. Years ago I checked out a carrier pilot in a C182. He said the hardest part of flying the 182 was having to flare the aircraft for landing. He explained that for carrier landings, they fly the airplane onto the deck with no flare. The 4G desired impact figure came from him. I seem to remember also that he said they want to catch the third wire.
Also, I believe the preferred terminology is "carrier traps" rather than landings, but I'm not certain.

I believe is not even refered to as a "trap" in many circles. More "controlled crash"

@Undo Poor wording on my part, and I'll fix that. When he was saying was that the hardest part of checking out in the C182 was to flair for the landing.

Pretty sure we're talking about "flare" not "flair". (slightly confusingly, also not "flare")

@ToddWilcox Good catch! I'm fixing that. Another senior moment on my part.

I was a passenger in a PA28 flown by a guy that forgot to flare.  It was quite the impact and I tasted blood.  Not enough to set off the ELT, which I'd imagine a 4G impact would.  I can't even imagine the kind of crash that is normal for carrier aircraft!

I have heard that one additional reason for the angled landing deck is:
If a plane somehow misses a landing, but does not have enough speed to take off, it will end up in the water slightly to the port side of the ship. The pilot can be picked up by a support ship. With an older straight deck, (if the deck was clear of airplanes - generally not the case), the landing plane would end up in the water directly in front of the carrier, and be run over by the carrier, and torn up by the propellers. That is not easy on the pilot. Such an overshoot has actually happened when an arresting cable slowed the plane below flying speed, but then broke. (I am not a pilot.)

Welcome to Aviation.SE! You're answer is good but could be improved with some references. Do you have a link to an article about the incident you mentioned?

Aeroalias covers the primary reasons the angled deck was introduced i.e. To facilitate the recovery of larger jet aircraft.  Back in WWII, flight operations aboard carriers would allow for one-way-in recoveries on the stern of the ship while aircraft were parked, hangared, or were launched from the bow.  Once the LSO gave you the cut signal, you pulled the throttle to idle and set it down on the deck.  In order to protect the aircraft tightly packed on the bow of the ship, you were going to either snag a cross deck pendant or go into a barricade near the ship's waist.  This is why the Eagle had 16 cross deck pendants and two types of barricades.  This was an inefficient, cumbersome and oftentimes destructive arrangement, especially when the plane could not snag a wire with the tail hook and went into the barricade and just became impossible by the time swept wing jets entered the fleet.
So it made more sense to provide an area where a recovering aircraft could touch down and be arrested to a full stop or add power and go around; this of course comes into direct conflict with the naval architecture of the carrier i.e. ships are designed as long rectangular structures and don't offer much lateral room from that to spare.  The only effective solution was to angle the landing area, giving a approaching jet a clear flight path to go around in.
And on the plus side it kept the bow clear and added extra deck real estate to launch jet aircraft from using the new and more powerful steam catapults (another British invention).  Positioning of the aircraft elevators on the port and starboard sides of the ship as opposed to the center of the bow gave even more space and alleviated congestion.

I'd prefer to avoid bumping into any of the catapults' pits so angling your landing through the superstructure sounds just peachy, regardless of how many super-steep-angled Chuck Yeager landings in mountain foothills you've ever approached (old timer instructors will grey your hair QUICKLY!)

can you please consider improving your answer? (proper punctuation and grammar, explaining why the catapult pits would be in the way, etc.)

Also you should quote the source for the image.

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Why would a Su-25, which has more power and is much lighter than an A-10, only fly half as high?
On the web, on several sites, the A-10 is listed with a ceiling of 14 km, the Su-25 with 7 km, although there is data that puts the height for the Su-25 at 10 km.
Nevertheless, why would the Su-25 fly only half as high as the A-10 knowing that the Su-25 has more engine power and is much lighter?

The data that puts Su-25 ceiling at 10 km seem to only have appeared when Russia tried to blame it for the MH-17 incident. The manufacturer (and it's Russian) lists 7 km.

TWR of a U-2 is about 30% higher than an A-10 but it flies another 7 km higher (the air at 21 km is about 3x as tenuous vs 14 km)

The data that puts the su 25 at 10 km pre dates the MH 17 incident by decades.  http://www.enemyforces.net/aircraft/su25.htm   http://www.military-today.com/aircraft/sukhoi_su25_frogfoot.htm

Because wing shape is quite different. Important parameters are aerodynamics. The engine performance at high altitude is important but not as important as aerodynamics.

I am with Manu on this one.  The goal of the A-10 was to be able to able to make quick turns to bring that big gun back on target after each strafing run, long loiter time over the target, and pilot protection and survivability.   It is design goals like this that drive the differences in aircraft design, and thus the performance characteristics.

in this video you can see in the cockpit the altitude indicating 8900 meter https://www.youtube.com/watch?v=GY_2NoHdNso

@Vido where in the video? Is 8900m the same as 10,000m? Does the plane have weapons on it? Easy questions if you think beyond the Russian propaganda ministry.

Just look at the wing loading: The Su-25 has between 585 kg/m² (regular Su-25) and 691 kg/m² (Su-25TK) when fully loaded, whereas the A-10 has a wing loading of 316 kg/m². This alone should explain why the Su-25 cannot climb as high.
Even when flying at minimum mass, the Su-25 has still 309 kg/m² (345 kg/m² for the Su-25TK), and the A-10 is almost a glider by comparison, having just 208 kg/m² at minimum mass.
Since both are subsonic designs, they have a strict limit on maximum speed. With that, wing loading and the airfoil determine their ceiling if thrust is sufficient.
Another limiting factor is the cockpit: Since the Su-25 was designed for ground attack, it has an unpressurized cockpit. This detail limits the certified envelope, even though a lightly loaded Su-25 can climb higher than 7000 m.

I may be mistaken, but you seem to be using the same logic one would use to assess automobile performance.  With a car, power to weight affects one of its major performance characteristics: acceleration.
With a plane, power to weight still affects acceleration performance and (ultimately) top speed.  But it has less to do with how high the plane can fly.  Altitude is determined by the design of your wing and at what altitudes the engines can function.
Remember, as you go higher there is less air. Less air means that the wing produces less lift, and it also means that the engines will often produce less power. You can compensate for this by other design means (like adding a turbo to the engine for example), but if you don't eventually you'll get to an altitude that you can't get past.
To be fair, both of these aircraft are designed for low altitude flying (ground attacks, mostly).  So it would be mostly pointless to fit a bunch of stuff to allow the craft to fly much higher than a couple miles or so.  Thus I'm willing to bet the engineers just skipped out on that stuff to save weight for other things (like guns, missiles, armor, etc).
This, of course, all assumes that the information being given out on the craft is accurate.  I'm sure it's all top secret, and I doubt Russia or the US are going to just hand out hard numbers.

jwenting commented that, in reality, the difference between high altitude and low altitude design generally has to do with optimization, not adding "stuff".  This is a great point, for some reason my head was thinking "turbo/supercharger" (which doesn't even make sense with jets).  I would maintain that, in many cases, you are adding stuff to get to a higher altitude (pressurization stuff, for example).
But, and this is jwentwings main point I think, when you look at the aerodynamics of an aircraft the main difference is a matter of optimization.  A wing that has good lift, good maneuverability and good stability at low altitude/speed, is not going to be so great at high altitude/speed.

given that the Su-25 was exported to several nations outside the USSR there's the option for independent verification of its performance characteristics.

The main problem with getting something suitable for both high and low altitude optimisation isn't adding "stuff", it's that the "stuff" you need for one is going to be less than optimal for the other. Can't very well fit 2 pairs of wings for example (to overcome that you can use variable geometry wings, but those have their own problems, they're heavy, difficult to maintain, and the wing box is large).

There might be some point in classifying performance data for newest aircraft like F-22, but A-10 and Su-25 are both quite old, sold to dozen or more countries and have been seen in many battles, so any potential adversary has many sources to verify their information. The published data are most likely correct.

@jwenting: With regards to wings, it just so happens that the A10 has wings that's optimal for both high altitude flight and low speed, ground hugging flight: large, high aspect ratio wings. So sometimes it can be done. The SU25 on the other hand gets away with having delta wings due to its low weight. The delta wings probably gives it an edge with maneuverability so like you said, it's a tradeoff. Which is always the case with aircraft.

@slebetman the Su-25 has no delta wings, it has slightly swept wings, of far smaller area than those of the A-10... You're confusing it with the Su-15.

@jwenting: http://upload.wikimedia.org/wikipedia/commons/thumb/3/32/Suchoi_Su-25.svg/280px-Suchoi_Su-25.svg.png - that's a delta wing. Albeit a high aspect ratio delta. The trailing edge is straight, not swept - hence delta

@jwenting: Even at high aspect ratio as in the SU25, a delta wing will have characteristics of delta wings - ability to retain aileron controls at high angles of attack, resistance to tip stalls on slow banking turns etc - this is due to leading edge vortex shedding which disappears when you sweep the trailing edge as well.

@slebetman get your terms right. It's not a delta wing... For a delta wing, see the Su-15, the Mirage III, the F-106.

Engines have different performance at different altitudes first of all. Additionally, I would suspect (I can't remember) that the SU-25 doesn't have pressurization equipment. Additionally, the wings on the SU-25 are smaller. An aircraft generating less lift can't fly as high, and this is likely the main reason.

You do not need a pressurized cockpit at 10 km, a oxygen mask will do, it is of course not as pleasant but it can be done.

"smaller wings can't fly as high". Tell that to the F-104 Starfighter...

@jwenting Of course that is true, but for our purposes, let's keep it simple.


text:
Can someone/something other than the pilot trigger the ejection seat?
Let's say there was a two-person jet (take the F-15 for example) that was involved in some sort of accident in the air that incapacitated the pilot (unconscious but still alive) and left the aircraft unflyable. Could the copilot eject his fellow pilot in an attempt to save his/her life from the inevitable crash that would eventually take place?
Is there some sort of system in the aircraft that would do this automatically?
Seems like an messy problem to have. On one hand you don't want to be blasted out the windshield accidentally by your copilot or faulty computer system but on the other hand it sure would be nice to survive in the off chance you are unable to exit the plane yourself.

Related: Does anything ever overriide a manual initiation. eg The "Starfighter" ejected downwards and at ;ow altitude HAD to be rolled inverted to eject safely.
[[German black joke of the period: Q: How do you acquire a Starfighter. A: Buy a plot of land and wait. | I was interested to find one, wheels set in concrete, in a coastal park in Taiwan, staring forever at the distant Chinese mainland and remembering.]]

In a word, yes.
There is a switch which controls this and the default position is "both".  If any handle is pulled (pull down over the face or the one between your legs), then both seats fire.  If solo, the switch is turned to "solo" so that the rear seat is not ejected and the front seat gets to leave a little bit quicker.  If the switch is left on solo and both seats are occupied, then each crew member can eject on their own.
You would also have if set to "solo" with an untrained passenger in the back.  You wouldn't want someone getting a bit excited and firing them both out of a perfectly working jet.
See this question about what happens, and this one to understand why you won't hit the canopy.
As far as I know, there is no computer controlled ejection system.  I don't think anyone would trust it to know better than the crew when it's time to bail out.

Interesting stuff. Do you know of any cases when a computer triggered ejection seat would have saved lives? I'm trying to think about what would the computer would look for...maybe a certain rate of descent below a certain altitude. But even then the pilot could be attempting a last minute landing/manuever. Thanks for the links!

Wait, you described the "solo" position as, the front seat pulls the handles, and the back seat doesn't eject, but then you write that with an untrained observer/passenger in the back, that's the position you'd use then also.  If an ejection is necessary, it seems unconscionable to leave the untrained observer to his own devices, instead of punching him out on the pilot's command.  Are you positive that your description hasn't over-simplified things a bit much?  Front-not-ejecting-the-back seems slightly different than back-not-ejecting-the-front...

@RalphJ : I imagine the back seat can be set to "solo" and the front to "both", so the pilot can eject the passenger but not vice versa.

@RalphJ The pilot can switch to both and eject the back seat passenger too.  The point is not to leave the back seat to their own devices, but to not allow the back seat to eject both.  I took a back seat ride in a Phantom (F4) and the briefing included ejection.  My seat was live if I pulled the handle but it would not eject the pilot.  He could however, eject me.

@codedude No I don't.  I can think of only one situation, which is were both crew are incapacitated.  But it's hard to think of how this could happen and for the ejection system to be still working.

@codedude I'm thinking also about "moral" issues. How many times pilots/crews decide not to eject because of the loss of lives the aircraft  could cause to people on the ground?

Probably not too often; the ground is big, and most military jets spend most of their time over sparsely populated areas.

@MarcoSanfilippo - Ejection is a very unhealthy experience.  A pilot doesn't consider ejection unless they expect that the plane will crash, with them, or without.

This guy had his untrained passenger punch out by accident. Hit that link for a nice photo of a Tomcat flying without the canopy.

@Simon The aircraft goes into uncontrolled flight that causes enough g forces to cause a blackout.  If the computer can determine that the recovery altitude is underground it should punch out the crew.  That would be a pretty rare situation, though.

@quietflyer, I see your point and rolled it back.  (I started with a comment, and edited reluctantly when I realized how old the question was, and that likely Simon might not be a regular any more.) I don't know how the F4 or F15 work, but I don't like the implication that the pilot could eject and leave a passenger in the plane.  That would not be possible in anything I've flown, and I can't imagine that's true.  I could discuss how the 4 seat Prowler worked, but I would have to dig into my old manuals to refresh myself on the 2 seaters that I have less time in...

This answer as it now stands after rollback may be accurate for some aircraft, but if so, it would be improved by a citation to an authoritative source.  An alternative arrangement is described here -- https://psemc.com/products/explosive-sequence-control/ , https://aviation.stackexchange.com/a/93617/34686 -- this allows a third option-- where pilot can eject self+passenger/GIB, passenger/GIB can eject self only, but passenger/GIB  cannot eject self plus pilot.

Yes. In general, the Weapons System Officer (WSO) can initiate ejection sequence and usually has control over it (of course it varies from aircraft to aircraft). From the interview of LCDR Joe "Smokin" Ruzicka, a F-14 Radar Intercept officer (RIO):

Both crew member's [sic] relied on each other- even down to the RIO having control of the ejection sequence- because conventional wisdom said the pilot would want to stay with the jet until it was too late.

Automatic ejection systems are rare, because you want the pilot to have control over when to eject (automatic ejection is considered a bad thing). However, it is found in a few aircraft, like the Soviet Yak-38, a VTOL aircraft. Once the aircraft rolled past 60 degrees in case of engine failure, ejection sequence was initiated automatically.

I wonder if there's any warning for the pilots before they are ejected...that's gotta be a rude awakening. :/

@codedude might be... But I guess in certain situations it might be better than wake up dead.

The conditions were much less trivial on Yak-38 than the roll angle. Roll could be handled manually; the real problem was increasing oscillations due to unbalanced thrust from the main and lifting engines. They feel benign at first but then develop rapidly, leaving no time to react and no way to recover. The system tried to catch these conditions, and exactly because of its non-triviality had quite a few misfires.

Not really an answer to the text and intent of the question, but with regard to the question as asked in the title ("Can someone/something other than the pilot trigger the ejection seat?"), I'll share a story that a friend who flew AWACS told me:
He was flying somewhere in the Middle East, and a Navy jet pulled up close enough to wave at the AWACS pilots, who weren't particularly amused.  Not knowing what frequency the Navy fighter was monitoring (if any), my friend in the left seat of the AWACS picks up his microphone, switches to Guard (which everybody monitors), and transmits something along the lines of, "Dude, we're putting out enough RF energy to launch your seat at that distance!"
The fighter peeled off in great haste.
So yes, something other than the pilot/s of the aircraft CAN potentially trigger the ejection seat.  I don't know how often this sort of thing has actually played out, but it has got to be an "oh, ****" moment if/when it ever did.

Hahah very interesting.

Seems like a possible weakness. Just blast a bunch of RF noise at a jet to bring it down?

@Steve Sounds like sarcasm and hyperbole to me for that very reason.  Also, AIUI the control systems for ejecting are primarily mechanical in nature so they'll continue to operate in the event of loss of power and would be inherently immune to RF as a result.  (Below melt/ignite the aircraft levels anyway.)

It was apparently an actual warning in the AWACS flight manual. Enought RF radiation can induce current in things like the iniator squibs, and the concern is that once the squib blows, everything else follows.  Remember, this is quite close to a massive emitter, and with enough power to see targets despite (some level of) jamming pretty far out, the inverse square law gives a HUGE amount of energy yards away (think, EMP types of effects). And while it clearly didn't actually launch THAT seat that day, the engineers said the risk was there.

@RalphJ Interesting. Are there procedures in place to ensure AWACS don't start their emitters on airport aprons etc. That could fry a lot of stuff.

@curious_cat r  Pretty sure they don't turn on the radar until they are in the air, for that reason & others (where it is optimized to scan). And I think they also confirm to the tanker crew that the radar is off before refueling.

@curious_cat if there aren't that'd be a major flaw in the operations manual for the aircraft. High levels of RF radiation and strong EM fields can have serious negative health effects (no, powerlines don't count). It's for that reason (among others) that there are wide no-go zones around radar transmitters, and the Faraday cage around your microwave oven isn't there for show either. An E-3 would definitely not want to have its transmitters turned on to more than idle power below a certain altitude.

@jwenting Indeed. One of the reasons for the "Personnel Working Aloft" call  on naval ships.

@Steve, "a bunch" in this case is "megawatts at point-blank range", enough to cause assorted EMP effects, and possibly cook the pilot.

@Mark: How do AWACS aircraft avoid cooking their own pilots (and other crew)?

@Sean  The radar is directional, so most of the power is in a beam pointing away from the aircraft itself. Beyond that, there is sufficient shielding to protect the crew from whatever stray leakage occurs.

@Sean, the aluminum skin of an airplane is a pretty good radar reflector.  The radar is mostly pointed away from the airplane, the skin reflects most of what's left, and only a little bit goes in the windows.  Contrast with what happens when a fighter pulls up alongside, with his cockpit windows pointed right at the radar.

The question as to whether other crew members can trigger the ejection sequence has been answered.
As to whether there can be automated systems that do it, the answer to that is a resounding "yes" as well.
The Yak-38 VTOL fighter of the Soviet navy had just such a system and they were considered for other types as well (but afaik never installed for reasons that will become clear).
This system worked. In fact it worked too good. It had a tendency to eject the pilot even when there was nothing wrong with the aircraft, causing more than a few aircraft losses and injured pilots as a result.
A system like that monitors the aircraft parameters and systems and when they go out of normal operational ranges for a certain period triggers the ejection sequence. With the Yak at least, it appears that putting the aircraft into a hover to land it would sometimes trigger the ejection, oops :)

It would end up landing...

@FreeMan: It might just as likely wind up seaing.

Something — yes, albeit not intentionally in this case: There was an accident in Sweden some years ago, in which a Gripen pilot was blown out of his aircraft because his legs and flight suit, affected by some high-G turns, actioned the ejection handle.
See Wikipedia and the Official report from the Accident Investigation Authority (PDF in Swedish).

Let's say there was a two-person jet (take the F-15 for example) that was involved in some sort of accident in the air that incapacitated the pilot (unconscious but still alive) and left the aircraft unflyable. Could the copilot eject his fellow pilot in an attempt to save his/her life from the inevitable crash that would eventually take place?

In some aircraft, it depends on the position of the "mode selector switch".
Here's how things work with the "mode selector switch" used in the  F/A-18, T-45, TAV-8B, and the two seat F-15:

Mode Selector Functions
NORMAL:  With the handle in this mode and initiation occurs in the front cockpit, both ejection seats will eject.  If initiated from the
rear cockpit, only the rear seat will ejection.
SOLO:  This mode is used when the rear cockpit is not occupied.  When the front cockpit pilot initiates ejection only the front seat
will ejection, reducing the time waiting for the aft sequencing to
occur.
REAR:  With the handle in this position both the front and aft ejection seats will eject, regardless of who initiates ejection and
the aft seat will always go first.

Obviously, the switch would only be set to the "rear" position if the rear seat were occupied by a crew member with enough training and experience to be trusted to know when to use the ejection system, and when not to use it!
Source: this web page from PacSci EMC, the manufacturer of the three-mode selector device used in the aircraft listed above.  (Interestingly enough, it's actually a pyrotechnic device.)

As requested - this post was substantially rewritten and references added in mid June 2022

Until recently the YAK38-B (maybe also YAK 36, and 141) were the only aircraft equipped with auto-eject.
The newer F35-B Lightning variant has auto-eject capability due to the existence of loss of vertical lift situations that can develop faster than a pilot may be able to manage. It seems likely that the logic which makes this desirable in the VTOL Yak 38 also applies to the F-35B. It will be interesting to see if the F35 designers have overcome the YAk's undesired auto-eject issues.

The British-made Martin Baker US16E ejector seat that equips the F-35 includes 3 airbags that inflate in a two-stage process to protect the head and neck of the pilot, wearing the heavy helmet packed with technology. The F-35B variant has a feature that will also eject the pilot automatically if it detects that the vertical-lift fan has failed (most serious during vertical landing but the fan is also in use during rolling take off). Loss of downward thrust from the fan would cause the aircraft to pitch down sharply, faster than the pilot could react to pull the ejection handle manually.
From: https://www.navylookout.com/salva

Various mentions of F-35B auto-eject capability. None of these are definitive but all are consistent:
https://www.pprune.org/military-aviation/643788-uk-f-35b-lost-3.html

A unique feature of the US16E is the trio of airbags that inflate in a two-stage process to protect the head and neck of the F-35 pilot, wearing the large helmet-mounted display, upon ejection. Also of note, the F-35B version of the Lightning II has an auto-eject mode. This is designed to function in the specific instance where the STOVL aircraft is in the hover, and the shaft-driven lift fan fails.

In that case, the jet is likely to pitch down sharply, quicker than the pilot can react to fire the seat manually. It will therefore fire automatically while the possibility of escape remains.

Synopsis of Lecture to RAeS Loughborough Branch - Martin-Baker: the JSF story so far 08 Mar 2011 Steve Roberts, JSG IPT Lead, Martin-Baker Aircraft Company Ltd

“...The ejection seat was required to be common to all three aircraft variants. It was also required to have superior ejection performance to all previous seats, meet new neck injury criteria and provide an auto-ejection capability when used in the F-35B (STOVL) aircraft. The last requirement demanded early firing of the ejection seat in the event of an aircraft malfunction in a manner similar to that used in the Russian YAK 36, 38 and 141 aircraft....

...Neck protection is provided by means of a “Catcher’s Mitt” inflatable device which supports both sides of the pilot’s helmet and also provides support to the top and /back of the helmet. This device is also held in a container located behind the pilot’s head. The device is vented before the parachute is deployed. The device has been tested & proved to inflate under simulated 50,000 ft altitude conditions....

...The F-35-B (STOVL) aircraft has additional failure modes associated with Lift Fan, Vane Box, Lift Fan Drive Shaft, Roll Duct and Turbine failures. A typical pilot takes two seconds to react to the ejection klaxon or one second if warned in advance of a likely failure. In the case of a STOVL related failure, ejection must take place within 0.6 seconds. Hence it was necessary to install smart failure sensors on the aircraft to automatically fire the ejection circuit mounted in the back of the seat....”

Material below re SU27 is retained only to allow prior comments to make sense. The Su27 does NOT have autoeject capability.
________________________________________
INTEREST ONLY MATERIAL BELOW HERE:
Added: This answer was based on advice I received that the SU27 had auto-ejection capability.
In a comment xxx states that the SU27 does not have auto-eject capability.
I have not yet obtained supporting factual references for either point of view. I will update this answer when I know more.
If the SU27 does NOT have auto eject capability then the crew members were extremely brave, regardless of what responsibility they did or did not have for the crash. I viewed a video of the crash and did a frame by frame examination from 1st contact with the ground by a wing until ejection.
The video speed was 25 frames per second.
The video was never "super clear" and became increasingly less so as the crash progressed (apparently due to the videographer attempting to not die).
From the time the wing 1st touched ground 4 frames (0.16S) elapsed until certain canopy motion was observable. It may have been starting to move for 1 to 2 frames before this.
The canopy was well clear by frame 8 (0.32 seconds post contact) and one crew member ejected at frame 11 (0.44 s post contact). The aircraft was moving out of frame but it appeared essentially certain that a prior ejection had not occurred so the 2nd ejection probably occurred some time after frame 11 (after 0.44s post contact).
While ejection initiation would have occurred at some time before frame 4 when canopy motion was first noticeable it would almost certainly have been a very short period prior, so it is very likely that the aircraft wing had touched the ground at or before ejection initiation.
That's brave.
Also stupid, if you want to live.
But very brave.
_______    End of addition.    ______________________________________
Yes.
This is a frame grab from a video about a Ukrainian airshow disaster when an SU27 crashed into the crowd with many fatalities. Both crew members ejected essentially "on impact" and I'm told that the ejections were automatically triggered. Both survived.
The ejection shown here obviously had to be preceded by a trigger, canopy eject, fire, ... sequence which I'd expect to last at least some "tenths of a second", so the actual decision point is uncertain.

Nope. They ejected manually. Su-27 doesn't have an automatic ejection system. There were quite a few airshow crashes involving Su-27 and MiG-29 with last-second ejections, esp. in 1990s, all triggered manually.

@Zeus See the addition to my answer. Have you any references to this - I'm happy either way. Something definitive would be nice to have. If it was manual eject then they were extremely brave (regardless of any culpability for the crash).

It would be a bit hard to prove an absence; perhaps you'll need to read the whole manual for Su-27 and/or K-36 (the ejection seat). I studied it well enough to know. The only Soviet (if not worldwide) operational aircraft to have automatic ejection was Yak-38.

My dad was a 30 year USAF officer. Spent 15 of them in Phantoms. There was an accident at Homestead AFB in the late 70’s where the ship had taxied out and taken the active runway and started lowering the canopies. Just as they sealed and locked either the WSO or PIC seat fired and he went through the Lexan or whatever it was. It probably killed him immediately, but if that didn’t then the fact that the seats weren’t 0/0 then sure didn’t help. It wasn’t an aircraft system though. A maintainer screwed up somehow. Or it was just a faulty part or whatever. Terrible way to go though.

Welcome to Aviation SE. This is posted as an 'answer' to a question about things other than the pilot triggering ejection but reads more like a comment. You appear to have an instance where an unintentional ejection occurred but no detail on how the event occurred and very vague information on when and where. To make this a useful answer recommend trying to pin down more details (date, which seat fired, why it fired) and remove as many of the 'whatevers' as possible by confirming what you can.

Go through is definitely the right word.


text:
for a piston-prop aircraft, why "V max excess power" equals Vmd and "V max excess thrust" equals Vmp?
as what i read from books, on thrust-velocity and power-velocity curves for a piston-prop airplane

V max excess power= Vmd

V max excess thrust= Vmp

these two values are just so clicking, and i couldn't figure out what's the physics behind it.

Power in aviation physics is Thrust × Velocity.  The best combination of these two is V max excess power, meaning (because of the drag curve) that no other speed will give a better rate of climb.
V max excess thrust is a slower speed because prop efficiency curve (thrust curve) declines with airspeed.  By slowing down, the greatest difference in thrust to drag is achieved (even though drag is slightly greater).  This allows the plane to climb at a higher angle, albeit at a slower speed.
V max excess thrust is also referred to as Vx, and V max excess power is Vy.

thanks for the answer! i entirely agree with what you said. but sorry for i didn't declare my question clearly lately, what i really wanna ask is why at a speed where an aircraft gets minimum drag gets maximun excess power, and vice versa.

@masterolof remember, "power" is Thrust × Velocity. At minimum drag plane uses least amount of thrust to counteract drag from lift, leaving all "excess" thrust to do things like climb.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Which airports have ILS Cat IIIC?
Are there any airports with ILS working CATIIIC?
What do the charts for this procedure look like? Is there a missed approach procedure?

This is not implemented anywhere in the world.
Wikipedia:

As of 2012 this category is not yet in operation anywhere in the world
  as it requires guidance to taxi in zero visibility as well. Category
  IIIc is not mentioned in EU-OPS.

Airliners:

As far as I know NO airport in the world currently offers catIIIc as
  it has the most ridiculous minima both in the horizontal and vertical
  plane ...

"In operation" and "implemented" are two different things. The second link suggest that many airports have the equipment installed to do a IIIc landing (although not IIIc taxiing), as it's similar/the same equipment from the airport end

Your "Airliners" source is not realiable since the explanation belongs to the year 2004, aprox. (http://www.airliners.net/forum/viewtopic.php?t=742695)

There would still need to be a missed approach procedure, since plenty of things besides "not seeing the runway/lights" can cause the need for a go-around: equipment malfunction, traffic on the runway, winds shifting out of limits, etc.  So no matter how "good" the approach is, it still has to have a defined missed approach procedure.
That procedure might well mirror the Cat I missed approach instructions.  Not certainly, but they often do.


text:
Can X-Plane be used as a professional simulator?
Can X-Plane be used as an actual Flight and Navigation Procedures Trainer (FNPT) level 1 flight simulator with Out The Window (OTW) visuals, separate Instructor Operation Station (IOS) and replica hardware?

there's the professional option when buying Xplane for setting up commercial simulator. Don't know how far it goes, or how far people have gone with it though.

Can you possibly clean up your question and write out what OTW and IOS stand for? Not everyone will be familiar with these terms. More information might be required for users to answer your question, too.

I am sorry, OTW means Out the window - visual sceanery- 120-180 degrees horizontal field of view and 60 vertical field of View . IOS - Instructor operating station - where instructor controls the simulation

@RekhaVenkatesh and FNPT?

related: http://aviation.stackexchange.com/questions/12634/how-close-is-x-plane-experience-to-real-flying

Have you seen this question? The FAA seems to have levels A-D, so what is "level 1"?

@Pondlife see the wiki link in that answer: numbers are for FTD, letters for FFS. Also 1-3 is EASA, 4-5 is FAA

@Federico Thanks, I didn't follow that link :-)

@Pondlife he applied the [tag:easa-regulations] tag, so FAA levels don't apply.

FNPT is Flight navigation procedure trainer

Maybe.
From the page linked by falstro above:

These include the ability to use cylindrical and spherical projection (as found in large simulators), and the ability to drive real Garmin 1000, Garmin 430, Garmin 430 WAAS, Garmin 530, and Garmin 530 WAAS units.

Pictures are included of a particular setup. The large projection format allows all-around visuals. The simulator can drive real Garmin devices, not just replicas. They recommend this vendor for FAA approved hardware (and for $2,100 I would hope a yoke could be FAA certified).
You can use an IOS even with the personal license for the simulator, on the same computer or a separate one.
X-Plane also explains that only the complete hardware+software combination can be certified for use as an FAA approved flight simulator. So it may be easier to just buy a package from a company like PFC, which has the combination already certified. They offer BATD and AATD simulator setups that use X-Plane.
If you need more information, you can contact X-Plane via the link on the same site linked above. They do not keep track of what people use their professional licenses for, but they may be able to comment on what level of certification is achievable.

To a limited extent, yes. Lower level devices such as an FNPT navigation trainer could be driven by an X-plane aerodynamic model and I believe some have achieved accreditation. For higher level devices such as the letter simulators, the issue is that the simulator model response must accurately match actual flight data. X-plane can get pretty good results from only a limited set of geometric data, however matching actual flight data is such a complicated multidimensional 3-D exercise that linearised assumptions are of very limited value.


text:
What does a "hard stand departure" mean?
I am reading a table explaining how to plan multiple diversion returns from an individual station:

widebody gate departures - xx minutes
narrow body gate departures - xx minutes
all hard stand departures - xx minutes

I am not a native English speaker and do not understand what a "hard stand departure" is.
Could anybody please explain this term?

A departure originate from hard stand instead of jet bridge at terminal?

A hardstand is a type of parking spot separate from the terminal.  Wide/narrow body gates are associated with the connection to the terminal, where a hardstand is just an area of pavement reinforced for heavy vehicles (or airplanes).


text:
How are regional planes delivered?
For example, E190s are produced in Brazil but operate in places like Germany, China, etc. Surely they can't fly these distances, so how are they delivered?


text:
Does the nose-up attitude of a jet make it more difficult to land than a turboprop?
Due to the more acute nose down attitude of a turboprop on approach, does this make it less difficult to control compared to the relatively high nose up attitude of a jet?

If I am not mistaken, the nose-down landing approach on turboprops has more to do with the high wing (and high position of the engines) seen on most western turboprops, than the engine type itself. I remember landing as a passenger in a Lufthansa BAe 146/Avro RJ85 jet, and the approach was definitely nose-down.

You should watch a CRJ-200 land sometime...

@casey I may well do that - Iberia has a few. Nose-down, as you say.

I find the heading and the question in the body a bit confusing. The heading seems to be about nose-up attitude of a jet, whereas the body seems to be about the nose-down attitude of a turboprop -- at least at first sight. So, I am going to edit the question make it less of a brain-twister. Hope you think it is ok.

You're asking, I think, two questions. The first in the title is very general; the second in the text relates to control as affected by aircraft pitch on the approach. The answers to both are going to be somewhat opinion based as well as depending on which turboprops and which jets you're talking about.
My thoughts are based on the following turboprops: King Air A90, Swearingen SA-226 and 227, Fokker F-27; and on the following jets: Cessna Citation 500, Boeing 727-100, and Boeing 747-100/200.
In my opinion, there is no general practical difference in the difficulty or ease of approaches and landings based on whether you're in a turboprop or a jet or what your pitch angle on the approach is. Some might say that a nose down attitude is going to give you better visibility. However, I never found that lack of visibility over the nose was a problem.
There are differences in the characteristics of turboprops and jets that make the one or the other the better approach and landing vehicle in certain circumstances. For example, if you need a quick descent, you can flatten out the pitch of a turboprop and get a lot of drag, more if you move into beta. For jets, the engines are always going to be producing some forward thrust (although I seem to remember the DC-8 allowed idle reverse in flight).
If you have a crosswind, the heavier the aircraft and the higher the landing speed, the easier it will be to handle the cross wind, and transport category jets in general are heavier than turboprops. Also, in a crosswind, a high wing is considered a liability, and there are a lot of high wing turboprops.
I guess what I'm saying is that individual aircraft and circumstances outweigh differences between turboprops and jets insofar as approach and landing is concerned.
The hardest and easiest aircraft I flew insofar as getting a good touchdown were both jets: the hardest being the 727-100 and easiest the 747.
The most flexible insofar as the approach was concerned were the SA-226/227. You could fly the approach clean at near-jet speeds and then slow down very quickly on short final. KSFO controllers back in the 1980s used to appreciate our ability to fit in. Or they could bring us in on a close-in downwind and then have us dump it for a well-timed turn to base and then a very short final.
---------- Edit for additional information
@JanHudec pointed out that turboprops have a faster response to power changes than jets. That's true, though in day to day flying, you plan for what you have. Obviously, though, in an emergency situation that required additional power, the turboprop would enjoy the advantage.
The difference in response to adding power is not as great as it used to be. As I remember, when the 727 first came out, there were a couple of incidences of 727s touching down slightly short of the runway because of the time required for the engines to spool up. The figure that sticks in my mind is that for those first engines, the time from full idle to full power was 7 seconds. Boeing fixed the problem by putting in a flight idle and a ground idle. The flight idle kept the engines spooled significantly higher than the ground idle. That involved no change to where you placed the thrust levers. You brought them all the way back. If you were still in the air, that wouldn't spool the engines all the way to full idle.
The 747 engines reacted very quickly, much more so than the 727 even with the flight idle setting. I remember two instances in the 747 in heavy gusting crosswinds where I used a lot of power at the last moment. In the 727 those touchdowns might have been a lot harder? In a turboprop maybe a little less hard?

Jet engines are known to respond to thrust setting changes rather slowly while turboprops respond practically instantaneously. Does it make make no difference in practice?

@JanHudec Good point! I'll edit that into my answer. Personally, I never had that make a difference, but I can certainly see where it could.

Turboprops have unswept wings of a higher aspect ratio than jets. This makes their lift curve slope steeper, so the pitch difference between cruise and touch-down is smaller for turboprops than for jets.


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How can an aircraft not fall into the sea after the arresting cable snaps during a carrier landing?
After watching that video, I can't fathom how in the world could the crew save the day. Can someone give the intuition on how did that happen?
Unfortunately, I am not in the aviation, but I recall from Flight Simulator that on landing, the aircraft has such a small value of velocity. Maybe the aircraft carrier was tall enough and/or wind was helping that day?

Carrier landings are done at full power until the aircraft stops completely (or even rolls back a bit), so they were at take-off power when the cable snapped. A good crew that knew not to pull up and stall helped allow them to pull out (but barely). The aircraft carrier is going at a good clip into the wind which also helps, remember, airplanes fly with air speed, not ground speed, so referencing the speed to the ship is misleading.

@RonBeyer didn't know that. Could you expand on why stalling helped, instead of pulling up? If it is big for a comment, then an answer would be nice, I think! Is it a frequent (relatively) accident for the cable to snap?

Stalling didn't help, they avoided stalling by fighting the urge to pull up. Keeping the nose down let them build air speed, which let them eventually climb out. I will add an answer tomorrow if nobody comes up with a good one. There used to be a carrier pilot around here but I haven't seen him in quite some time.

Yes I understand that, thanks! @carrierPilot come aboard! :)))

And yes, its not unheard of for the cable to snap, that's one of the reasons why its done at full power. Missing the cables also happens once in a while and you don't want to be idling when you hit the deck if that happens, especially with spool up times for some engines.

The truth of the matter:  That E-2C pilot escaped crashing by a hair's breadth.  He was just very, very fortunate that the combination of holding full power, the position on the flight deck where the arrester pendant failed allowing for a small takeoff roll to accelerate, plus the 40+ ft drop off the deck of the ship to the waves combined with the ship steaming into the wind was enough to gain him the end airspeed he needed to fly again.  The flight crew received the Air Medal for their heroism in the face of that situation.  As an E-2 does not have crew stations equipped with ejection seats, there was no other option available to the flight crew than to attempt to gain airspeed and hope for the best.  That cross deck pendant failure could have easily resulted in disaster and most pilots in that situation don't live to tell the tale.
Although it is rare, cross deck pendant failures can and do happen and are extremely dangerous, both to the aircrew of the recovering aircraft and to nearby flight deck personnel; there have been cases where a failed cable has literally sliced a man in half.  As a precaution, each cross deck pendant has as pre-set service life of 100 traps, then it is removed from the purchase cables on the arresting gear and destroyed.
This video was shot by an sailor aboard the USS Ronald Reagan during sea trials in 2003.  The arresting gear failed, sending the aircraft over the edge of the deck.  The F-18 pilot ejected and survived.  Note the amount of damage which the end of the cross deck pendant does to equipment and personnel as it whips across the flight deck.

You have a (rough) ratio for your last claim?

What do you mean?

@gsamaras: Do you mean the ratio of "there have been cases where a failed cable has literally sliced a man in half" ?!

@gsamaras According to Wikipedia (which at least should give a rough indication), there were three incidents with the arresting cable in the last 16 years. https://en.wikipedia.org/wiki/Lists_of_accidents_and_incidents_involving_military_aircraft

According to a comment on the E-2C video, there were 8 people injured when the pendent snapped.

I mean exactly what @Sumurai8 said, thank you!

He must have been very lucky.
One more factor that I can think of is the end of the ship's deck were he run off to must have been rocking up and down with the waves and was at the optimal position which is just short of end of swinging up at the high elevation and a few degrees up tilt and hesitate a moment before swinging back down.
Effectively discharging the plane with a bit of climb momentum and several feet higher above the water.
The fact that the tail of plane didn't scrape the deck supports this theory.
Pilot must have done a perfect job of easing the yoke first and hugging the water to take advantage of ground effect.

I am not familiar with the ground effect unfortunately, can you give the intuition of it, in simple words? Also, when you say "rocking up end down", you meant "and" instead of "end" maybe? :)

The ground effect is the fact that airplanes gain lift when near the ground. Some vehicles rely on the effect entirely for flight.

Sorry, yes it was "up and down." Ground effect is when the plane is flaying near the ground barely a few feet hi, there is a cushion of pressure that gives the wings additional lift!


text:
Amazon Atlas nose-down elevator deflection?
In this link I read about the crashed aircraft:

The airplane then pitched nose down over the next 18 seconds to about 49° in response to nose-down elevator deflection.

I feel that this is a common mechanism, unknown to non-expert, like me. What does it mean?
Interested in a rather intuitive, relaxed explanation, rather than an analytical one.

There are a few words in that description which might seem a bit technical to a lay-person.
The word "pitch" refers to the angle of the aircraft, either up or down.

pitch: (of a moving ship, aircraft, or vehicle) rock or oscillate around a lateral axis, so that the front moves up and down.

"49°" refers to the angle from the horizontal (0°). 49° is a very steep decent. Much more so than a normal descent profile.
The "elevator" is the control surface used on an aircraft to control the pitch, either up or down. So "nose-down elevator deflection" says that the elevator position were such that the aircraft is pointing down. The implication/possibility is that the controls in the cockpit were commanding that input, or that a mechanical fault caused the elevators to do so.

"Nose-down elevator deflection" is a long winded way to say the elevators moved in the direction that would push the aircraft into a dive.  It's phrased this way because it isn't always clear from flight data recorders whether this was a commanded (pilot input) movement, or uncommanded.
In either case, the elevators were deflected downward, which pushes the tail up and the nose down, and over a fairly long time (in terms of a crash in progress) the aircraft was nosed down by 49 degrees.


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Aircraft Turns - is there a 'pre-turn'?
I've travelled from Vancouver to London often enough to see this phenomenon as something that happens regularly enough to notice. I'm just not sure why.
So... the route from Vancouver to London is basically a series of right-hand turns. I guess it follows a set of rhumb lines or whatever. But what I noticed was that most right-turns are preceded by a smaller left turn.
ie the aircraft banks and turns left for a couple of seconds, then straightens up and goes straight into the longer right hand turn I'm expecting.
So my question is, why does it do that little turn in the opposite direction? I can't imagine it's navigational, not when it's cruising at high altitude. Is it something mechanical? Say to make sure everything is working and not iced up? I imagine the aircraft is on autopilot at that point, so it's not a pilot thing.
Does anyone know what this is? In fact, has anyone else even noticed this?! I think I've noticed it most on Vancouver-London because when you're over Iceland and the aircraft starts to turn north, you start to wonder where you are headed!

Can you give a specific flight and date you noticed it on. When we get questions like this it often turns out to be mild spatial disorientation and the aircraft is not really doing what it feels like from the cabin.

I can't, no. Do you think the flighttrackers would pick it up? Sorry. It's a question I've wondered for a while and just found this forum today. I don't think it's disorientation, or that I imagined it. I always get a window seat so I can see that we are banked to the left.

It highly depends. If you look at the flight data on, say FR24 it is usually very irregular. Sometimes you get a gps fix every 60 seconds, sometimes it's every 10 minutes. I was thinking if someone looked at a flight path they might see something specific. It could be like ymb1 says, just a momentary correction for wind that just happens to precede a turn. It could be a delayed reaction from the yaw damper, or even the yaw damper working too quickly making the rudder move before the wings. There really is no reason to bank one way before turning the other way.

They may be doing S-turns for spacing.

It would be helpful if you could give us more details about how much the airplane banks to the left and how much the airplane changes heading to the left (north).

It's hard to say how much the heading changes. I'd say a 10 degree bank to the left for about 5-6 seconds. Definitely not just a reaction to buffeting, but a recognizable turn. Or so I perceived it. As others are saying, it could be a trick of the mind. I don't think it was, but who knows?! What I do know is that you'll all probably be looking out for the same thing the next time you fly! If it happens - you know where to come! ;-)


text:
Has this Google Maps imagery of 4 planes on a runway been tampered with?
The image below is of Google Maps (30 May 2018) of Amsterdam Schiphol's Aalsmeerbaan (36R).
It shows 4 planes on the runway and a fifth that's about to land. When you zoom in, all planes seem identical.
Has this image been tampered with or could there be an explanation for this?

Just a note, but tamper strongly implies some kind of unauthorised/unlawful/nefarious alteration. If the planes aren't actually there, it's far more likely to be some kind of post-processing artefact rather than some kind of deliberate tampering.

By the way it is a good catch!!

If those are actually different planes, then the controllers at Schiphol are utterly failing at maintaining separation.

Sattelites photography are usually not actual photos but rather a compilation of multiples photos not necesserally taken at the same time.

@ManuH A lot of Google's photography is aerial rather than satellite. However, you're correct that it's not taken at the same time. The aircraft or satellite would fly in a line taking photos which would later be stitched together.

Link to the Google Map in question:
https://goo.gl/maps/KmtDUB4x7VK2

Didn't you know? The Netherlands has a group of 787s that not only do formation flying, they also do formation landing...
No, it's not a thing, but I want it to be a thing.

Link to a question on the Photo.SE site about the same image: https://photo.stackexchange.com/q/95153/9161

Looks like Google's new 3D imagery satellite is in operation...

Some people have marked this question as off-topic.
In my opinion this question only becomes off-topic after you know the answer. I'm not sure if that should make the question off-topic.

Personally I agree with the general assessment that this is off topic. you're asking "has been this image tampered?" i.e. something a informatic forensic investigator should answer, not a pilot or a mechanic.

True, point taken

It was on Photo.SE last December. The question got 200 views, seven votes and the best answer also seven. I guess aviation types like photos better than photographers do. Of course, they were looking at red channel mismatch instead of 'tampering'.

Since that's the date you saw the planes on Google Maps and not the date of their actual existence at the airport, I think writing down the date isn't really important.

Google Maps and Google Earth are made by stitching together many different images to create the illusion of a single massive picture of the globe.
The image you are seeing was almost certainly made by an aerial photography plane passing overhead of another plane landing.  In multiple snapshots, it captured the same plane on final, touching down, rolling out and stopping.
The images were assembled together to line up the ground and all static elements.  But items that are moving appear multiple times in different images.

Your answer makes so much sense that it makes me wonder why I didn't think of it myself. The spacing between the planes also supports your answer. You can actually see the plane slowing down.

I would have thought it might be satellite photos, but the same principle applies.

@CptReynolds Google uses satellite imagery when you're zoomed out and aerial imagery when you're zoomed in.

The southernmost plane in the sequence is also still in the air, so would never happen IRL (wake turbulence, ATC rules, etc). Someone could do some fancy math, assuming a 140 kt landing speed and confirm it's a satellite (and that there's one aircraft image missing from the stitching of the images.

@IanW It's most certainly aerial photography, satellite photography simply does not have an adequate resolution for images like these. Wake turbulence only applies to directly crossing the flight path; ATC requires something like a 2000ft vertical separation (my guess is that the surveyor flew at 7000ft, as flights at Schiphol are generally initially cleared to 6000ft)

Looking at the zoomed-in image, it's pretty clear that the survey plane takes three images (RGB) with three filters and then they are stitched together to get true colour - of course the stitching fails with a fast moving object.

No matter who or what took those photos... The amount of paperwork to get permission to take them above an big airport in full operation must have been epic.

When going back further, you can see the plane a sixth time.

@Tonny Not necessarily.  In the US, the airspace over major airports isn't restricted at all altitudes. At the major airports around New York City, the class B airspace only extends to 7000 feet

@Sanchises: satellite photography simply does not have an adequate resolution for images like these -- commercial satellite tech, sure. But spy satellites can probably do even better.

@mgr326639 There is whole class of jokes about google image stitching, eg look up "stealth train uncloaks"

@MattD Those photos are from Schiphol (AMS). Airspace there is very tightly controlled. When I was still flying sport and small business planes (20 years ago) it was a major pain in the a** to get permission to overfly the airport. Getting landing clearance was actually much easier so I got in the habit of making a short stop at AMS as part of the Amsterdam sightseeing flight. Since AMS only got busier and noise/environment regulations (which restrict flight corridors) stricter I image getting clearance now is even more difficult.

@MartinBonner that could be, but to me it looks like a classic case of Chromatic Aberration https://en.wikipedia.org/wiki/Chromatic_aberration which is a physical effect that occurs in the lens of the camera.

I'd also like to point out that some pains have been taken to digitally alter roads and highways to remove all vehicles.

@JaredK - oops!  I think you are right.

@reirab: Do you know if there's a way to force switching between aerial and satellite imagery? There used to be a few years ago, but I'm not sure anymore.

@Mehrdad Not that I'm aware of. For me, it usually just switches at a certain zoom level (at least in the areas where aerial photography is available at all.)

@JaredK I definitely think it's a multiple-exposure effect, not chromatic aberration. See https://chat.stackexchange.com/rooms/78317/chromatic-aberration-or-multiple-exposures

This is a common occurrence with airplanes on Google maps. Google overlays multiple scans taken seconds apart from satellite imagery to get the best image quality.
This works very well for stationary objects, such as buildings and land structures but results in multiple images of high speed objects, such as airplanes. Sometimes this effect is visible even with cars on a highway.

What looks like tampering is actually multiple exposures, plus cross-channel rolling shutter (the color fringes).  If you measure the spacing of the aircraft images and the size of the fringes, you can infer that it's one aircraft slowing down after touchdown.  You can even see the puffs of smoke that show the main gear touching down before the nose wheel.  Here's a careful analysis.


text:
How should this Bendix course deviation indicator from the '50s be read?
This is a Swissair photo from a DC-7C panel.

Source
I have seen photos on airliners.net of these in DC-6s, VC-118 and Constellations. It appears that other companies besides Bendix made these indicators, but they are similar in appearance and function.
I've searched unsuccessfully for patents, or any other information that would describe what I am asking about:

What are these "45" scales for?
What is the flag in the window used to indicate?
What are these two lines for?
What happens when the test button is pressed, e.g., the loc, glideslope needles move to some position, #5 rotates to some position, #2 flag appears?
What does this "airplane" indicate?

If that helps, the reference is MN-97

@mins yes it does! Amazing what you can find when you know what to look for.

This is an early version of an HSI.  The heading (depicted by the airplane) is either set manually, or it's slaved to a remote compass.
Responding to the question as numbered:

Depicts wind correction angle when tracking a course.
To/From flag
Glide slope reference (too low)
Push to test the warning light.  Also push to illuminate while turning to adjust brightness.  This may light without a valid heading source from a remote compass/flux valve.  It may also be to indicate failure of an internal gyro if so equipped for heading source.
Depicts aircraft the heading

As the sticker indicates "OMNI-MAG" this should be the compass version.

That large cannon plug leads me to suspect it's indeed coupled to a remote compass.  The name "OMNI-MAG" is descriptive that the indicator displays a composite view of VOR course and magnetic heading data.

Here are a couple of links to some further information about the MD-97: (https://www.flightglobal.com/FlightPDFArchive/1957/1957%20-%200495.PDF) and  (http://www.timetravelair.com/techlibrary/EO%2005-45B-1A.pdf)


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Where can I find examples of ADS-B surface (ground) position data?
To check my decoding it would be helpful to have some correct reference data for checking input and output as follows:
Input: 19-bit Compact Position Reporting (CPR) even latitude and longitude / odd latitude and longitude (decimal values are OK)
Correct output: Latitude and longitude in degrees (decimal)
Where can I find sample data that I can use for testing?

Hello Hans, welcome to aviation.SE

The best source for that data would be EUROCAE Document ED-102A or RTCA Document DO-260B. These are the Minimal Operational Performance Specifications for ADS-B on 1090MHz. They include all the requirements on the ADS-B transmitter, including test data to demonstrate that the requirements are met.
However, if you don't have access to those documents, you can try and receive some ADS-B messages from aircraft on the ground using an ADS-B receiver and decode those. If the surface position messages indicate good position integrity (format type code 5, 6, 7 but not 8) and the decoded positions appear on airport paved surfaces consistently than you are sure that you've got it right.
Note that ADS-B surface decoding is not globally unambiguous; you need to know where approximately the receiver is (as in which N/S,E/W hemisphere) to unambiguously decode the surface position message.

The table below shows some encodings that can be used to verify wether your surface CPR decoder works.
The first four columns show latitude and longitude (in decimal and 32 bit angular weighted binary hexadecimal notation), the next 6 columns show the CPR data.
\begin{array}{|c|c|c|c|c|c|c|c|c|c|}
 \hline
 \text{Latitude}&&\text{Longitude}&&\text{Lat.}&\text{Lon.}&\text{NL}&\text{Lat.}&\text{Lon.}&\text{NL}\\
(Decimal)&(HEX)&(Decimal)&(HEX)&(HEX)&(HEX)&(Dec.)&(HEX)&(HEX)&(Dec.)\\
 \hline
-27.93897726&EC21DD4A&153.00998&6CCE9DE7&0BF7F&03636&53&15E70&0CFC1&53\\
\hline
27.938976&13DE22A7  &45.0000&20000000&14081&10000&53&0A190&00000&53\\
\hline
\end{array}
source: EUROCAE ED-102A , table 2-214 (truncated), page 699

Hello DeltaLima, thank you for your answer. However, what I want is some matching data, i.e. cpr data with corresponding (correct) latitude/longitude values.

Hello @HansMuschik, I have the data you are looking for somewhere, but I need to dig it out the archives which will take some time. Alternatively you can provide an odd/even surface squitter pair (from the same aircraft, transmitted within 10 seconds from each other) and I'll decode it for you.

Hello DeltaLima, thank you for your support. Actually, it’s the other way around - testing a program which produces cpr values for irs data. Out of interest I looked into the cpr calculations and wrote a script mimicking the conversion in both directions. For coding I used the specified algorithm, for decoding available snippets from the internet. For air I found example data in the net, but until now not for ground. For Lat = 50 and Lon = 15 I calculated ground cpr even: 174763, 305835 and ground cpr odd: 101945, 283989. My decode then results again in 50/15.

@HansMuschik, I will run it though my software tonight and let you know. Out of curiosity, what is irs data?

Inertial reference system, more commonly known as an inertial navigation system

@HansMuschik That is interesting. Are you building a transponder / ADS-B transmitter? Why would you use IRS as position source for ADS-B? IRS does usually not provide integrity, so the ADS-B data can't really be used (NIC will be 0).

I'm not building anything. I want to verify my script cpr <-> lat/lon to have correct data for testing an existing software.

@HansMuschik I've ran the values provided by you through my software.  Bad news: they are different from the output of my coder / decoder. FWIW I consider my software correct; the CPR codec passes the relevant tests of ED-102A / DO-260B.


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What is a localiser back-course approach and how does it work?
What does back-course approach mean ? How much signal strength should the back lobe of ILS should have in order to trace it and commence landing. How common is this type of landing for a pilot. What all instruments are required for this type of landing?

Hello Huntkil, welcome to Aviation.SE

A localizer back course is simply flying on the back side of the localizer to the runway.  How a localizer works is it sends out two signal lobes:  one at 90Hz and the other at 150Hz.  The localizer needle in the airplane compares the relative strength it receives from both lobes and then shows a deflection.
See this figure from the Instrument Flying Handbook (2015) published by the FAA.

Notice the top left of the picture shows the same lobes on the same side of the runway.  Now imagine flying the front-course, the blue lobe is on the right.  If you are flying the back-course, the blue lobe would be on the left.
The localizer needle doesn't know if you are on the front-course or the back-course and will show the same deflection for both situations.  The problem comes in for the back-course is that the needle deflection is deflected the wrong way.

To answer your questions.

What does back-course mean?  It simply means you are flying on the opposite of the localizer signal.  If there is a back-course published, the signal strength will be strong enough to fly the approach as required.
How common is a back-course approach?  There are currently 69 back-course approaches in the United States.  There are approximately 1,893 ILS approaches.  This is around 3.5% of back-course approaches as compared to ILS approaches.
The same flight and navigation instruments required to fly a front-course ILS is required to fly a back-course ILS.

From a technique standpoint.  Whenever I fly a back-course approach, irrespective of whether I am using an HSI or VOR receiver, I will always set in the front course.  For pilots that use an HSI this will provide for "positive sensing" meaning the needle will deflect correctly.  For pilots using a VOR, the needle will shade bottom numbers that correspond to heading that need to be flown to get back onto the back-course approach.

If this was a back-course approach, notice that the needle is deflected to the right.  Conventional wisdom says you need to turn away from the needle to re-intercept.  I say to select a heading under the needle to fly.  That heading will be approximately 120°.  Take a look at the heading indicator and determine that you most likely need to turn left to re-intercept the back-course.  Try it and you will see it works.  Conversely, I also teach the same concept for an ILS except the heading to fly is on top of the VOR indicator instead of on the bottom.